[HN Gopher] Outdoor Sound Propagation in the U.S. Civil War ___________________________________________________________________ Outdoor Sound Propagation in the U.S. Civil War Author : sdenton4 Score : 72 points Date : 2022-08-21 17:53 UTC (5 hours ago) (HTM) web link (wesclark.com) (TXT) w3m dump (wesclark.com) | balentio wrote: | This is a not widely documented Civil War phenomenon, but happens | probably quite often without people knowing it since by | definition, it is the ABSENCE of sound that has to be noticed. | jchanimal wrote: | Similar historic outcome. I was in the room for Howard's Dean | "scream". which basically ended his campaign. As far as I can | tell the cause was not enough attention paid to the microphone | sound reinforcement. He had to push too hard to be heard in the | raucous room. | arminiusreturns wrote: | I'd like to find the history of declaring that scream ended his | campaign. Since you were there, did anyone in the crowd react | in that manner afterwards, or was it really just an excuse the | media used to lambast him artificially (which is what it felt | like to me)? | chrisseaton wrote: | Did it sound weird in the room, or was it only on the | recording? | [deleted] | Domobran7 wrote: | That is really interesting. Honestly, I had never even thought | about it until now, but now it reminded me of how Titanic may | have sunk due to fatamorgana. | | Weather really does play major role in human history, even when | you don't see or expect it. | balentio wrote: | prenoob wrote: | OT but related: if the subject matter is of interest to you you | may enjoy this book -> | https://www.google.com/books/edition/Battlefield_Acoustics/O... | hirundo wrote: | If your network is good enough to gather a microphone's data from | each soldier/drone on the battlefield, you could centrally | assemble a very accurate location and type on any weapon fired | and other ambient sound. That data could be used to evaluate | risks and return fire accurately within milliseconds. It could | give a general a lack of fog-of-war only available before in | simulations. | bragr wrote: | I'm not sure this is true given the inaccuracy of shotspotter | h2odragon wrote: | I think shotspotter's problems are more political than | technical. | | Not to say they don't have technical challenges too: better | _sensors_ than the human ear turn out to be fairly easy, but | interpreting that data is still hard. Brains are complicated, | "hearing" is a process contributed to by nearly every layer | of meat that reacts to sound. The human ability to notice a | new noise in the cacophony of everyday life is really an | amazing trick if you think about it. | sdenton4 wrote: | I know a non-shotspotter effort to identify gunshot sound | in a very different context which also is having a very | hard time; there is a real unsolved technical problem here. | And it makes me think that ID'ing gun model from audio - | which will be harder than simply identifying the existence | of gunfire - is going to be very difficult. | livueta wrote: | Yes, but with caveats. Disclaimer: just a hobbyist, not my | professional area, corrections appreciated | | - oldschool radio direction-finding with a couple of | directional antennas that are manually positioned and rotated | (i.e. based on signal attenuation) doesn't really work for | point-in-time things like a single brief signal unless you have | massive arrays of well-positioned receivers, which is fine if | you're building an HFDF installation but not fine if you're a | squad on the move | | - multilateration on the basis of signal attenuation, analogous | to that sort of oldschool RDF, is possible but IME doesn't | perform very well; same problem where you often need a lot of | well-positioned points to shrink the possibility envelope down | to something useful | | - multilateration on the basis of time of arrival, analogous to | more modern pseudo-doppler / correlative interferometry RDF | techniques, can perform a lot better but requires a very high | quality shared time source - if the model is analyzing info | from an array of observers, this can be a problem on typical | battlefield network designs that prioritize availability over | performance - but this approach also enables single site setups | where a local time source and a handful of receivers can read a | bearing without actually needing to network at all, though this | involves a lot of math | wbl wrote: | GPS solves the sync issue to the order of nanoseconds. You | can also have local TOA determine angles that get passed up | to triangulate. The US Army deployed some of these techniques | in antisniper work in Iraq. | livueta wrote: | That's a good point, and required time precision seems like | it should be proportional to the velocity of the signal | being investigated. I had some bad experiences trying to | use gps time for RDF, but that might not apply here. | | From https://www.usenix.org/legacy/events/mobisys07/full_pa | pers/p... | | > Our time synchronization approach yields errors signif- | icantly less than 100 microseconds. As the sound travels | about 3 cm in that time, time synchronization errors have a | negligible effect on the system. | | Sounds like it? | | The anti-sniper systems I knew about already (Boomerang) | are that single-site setup where time sync isn't a problem. | The "Individual Gunshot Detector" sounds more like what | you're describing. | | > The Individual Gunshot Detector (IGD) by Qinetiq consists | of a shoulder-mounted unit with four acoustic sensors and a | chest display that attaches to body armor. | | Still looking for more detail, but that sounds like a local | ToA > pass up angles for triangulation type deal. | galangalalgol wrote: | I read an ieee journal article over a decade ago claiming | success with helmet mounted sensors. The system used the time | of the sonic crack and the muzzle report as observed from | each helmet. Its like GPS, if you have 5 or more observers | you can solve for the time reference as well. Actually, it | might be less since they had multiple observations from each | helmet. It supposedly could then highlight the location of | the shot using AR. It then went on to say they could tell | what the firearm was from the muzzle report. Can't find the | article now. Doesn't seem that outlandish, but as you say, | accuracy would be the real question. The speed of sound can | vary so much based on weather. | livueta wrote: | Maybe this? https://www.usenix.org/legacy/events/mobisys07/ | full_papers/p... | | > It then went on to say they could tell what the firearm | was from the muzzle report. | | > over 95% caliber estimation accuracy for all shots, and | close to 100% weapon estimation accuracy for 4 out of 6 | guns tested. | | That's pretty cool. Gotta read the whole thing now. | | e: kinda relevant to the other subthread about time sync: | | > Correlating ToA measurements requires a common time base | and precise time synchronization in the sensor network. The | Routing Integrated Time Synchronization (RITS) [15] | protocol relies on very accurate MAC-layer time-stamping to | embed the cumulative delay that a data message accrued | since the time of the detection in the message itself. That | is, at every node it measures the time the message spent | there and adds this to the number in the time delay slot of | the message, right before it leaves the current node. Every | receiving node can subtract the delay from its current time | to obtain the detection time in its local time reference. | The service provides very accurate time conversion (few ms | per hop error), which is more than adequate for this | application. Note, that the motes also need to convert the | sensorboard time stamps to mote time as it is described | earlier. | MichaelCollins wrote: | > _within milliseconds._ | | I think you're overestimating the speed of sound a bit. You'd | need nearly 5 seconds to hear artillery fire a mile away. | polishdude20 wrote: | "Guns fired at the funeral of Queen Victoria in London in 1901 | were heard in Scotland" | | Wait how is this possible? | MichaelCollins wrote: | Probably the atmospheric version of SOFAR; thermal layers in | the atmosphere acting as a wave guide for very low frequency | sound waves. In the ocean, the sound of explosions can travel | thousands of miles in the SOFAR channel. | | https://en.wikipedia.org/wiki/SOFAR_channel | bee_rider wrote: | It seems a bit odd, huh? | | I found on google: | | https://www.latimes.com/archives/la-xpm-1999-jun-24-me-49796... | | Interestingly similar phrase: | | > Guns fired at the funeral of Queen Victoria in London in 1901 | were heard in Scotland, but not across a wide region in | between. | | > Guns fired at the funeral of Queen Victoria in London in 1901 | were heard in Scotland, but not in wide areas of northern | England. | | Searching the exact phrase | | > "Guns fired at the funeral of Queen Victoria in London in | 1901 were heard in Scotland" | | Turned up a couple sites, one from the national academies press | | https://nap.nationalacademies.org/read/25226/chapter/3 | | but it appears in a "background" section of a work on highway | engineering, not cited. | | The other sites seemed like maybe sketchy textbook sharing | sites, so I didn't check them out. | | Seems like maybe a popular bit of questionable trivia? | schmendreck wrote: | analog31 wrote: | Less background noise, and better hearing, may have been | factors. | stevenwoo wrote: | Weather inversion where the sound the travels slightly faster | and farther in different temperature air medium plus reflection | of waves that would normally dissipate to upper atmosphere if I | read this correctly. http://spectrums.com/sound-and-the- | weather/ | [deleted] | duskwuff wrote: | In this context, "guns" probably means cannon, not small arms | like rifles or pistols. | bragr wrote: | Even still, cannon fire from 250+ miles (at least, that's | just to the border) seems improbable | R0b0t1 wrote: | Seems plausible base on my experiences outdoors, but it | heavily depends on ambient conditions. Over such large | distances I think the unlikely part is you do that trick | twice, but even that is plausible merely by looking at | seasonal changes. | vidanay wrote: | And there's my weekly reminder that the British Isles are | SMALL. | galangalalgol wrote: | No kidding! I was on the interstate this last week and a | sign showed more than twice that distance just to the | next major city in the state. (along that highway, there | were closer ones in other directions) | pessimizer wrote: | There's a saying that goes something like "Americans | think 100 years is a long time, and Europeans think 100 | miles is a long way." ___________________________________________________________________ (page generated 2022-08-21 23:00 UTC)